Youth Hostel Association (England and Wales) Limited

Structural Inspection Report YHA HOSTEL ILAM HALL ASHBOURNE

Date: 9 July 2014 Prepared by: P A Hucks Reviewed by: P A Hucks Project No. 1617 BRIEF

At the request of Youth Hostel Association (England and Wales) Limited, Summit Consulting Engineers Limited visited the Hostel at Ilam Hall, Ashbourne in the Peak District in order to undertake a structural visual inspection of the external rear corner piers of the property and prepare a report with conclusions and recommendations where possible.

INTRODUCTION

The property was a substantial detached property built we understand around 1820; records indicate that this building replaces an earlier building constructed in the 16th century; the present building is significantly reduced in footprint as the original 1820’s building suffered severe fire damage in the 1920’s and subsequently underwent refurbishment works with the former main area of the building being demolished and the remainder subject to the refurbishment utilising, it is understood, salvaged stone work from the former larger building.

The property is understood to be a Grade II\* Listed Building and is currently owned by The National Trust.

Since the mid-1930’s, the property has been used as a hostel.

DOCUMENTS PROVIDED

We have been provided no drawings of the property; we have however been provided with copies of some historical photographs of the property.

Attached to this Report in Appendix A are copies of these relevant documents. INSPECTION

On 9 June 2014 we attended the property in order to undertake our visual structural inspection.

During the course of our inspection we did not cut in to the fabric of the structure nor did we enter any inaccessible roof or floor areas and our Report should be based in this light.

Where left and right hand sides are indicated in this Report, they are given at all times as viewing the property from the front with the main entrance within the Porte Cochere being located at the front left hand corner on the north elevation.

Ground level around the property fell generally from the right to the left; the rear external levels beyond the building were elevated forming a terrace. The property was surrounded with trees but these were noted to be sufficiently distant so as not to be influential on the stability of the building foundations.

During the course of our inspection we noted the following items which are relevant to our Report and photographs are included in Appendix B of this Report:

External

1. On the rear (south) elevation of the left hand wing we noted the corners were formed with unorthodox sandstone piers which projected beyond the faces of the main building line and ashlar panels. The piers terminated below the upper parapet wall string course with no apparent finishing block to disperse any surface water that may collect on this “ledge”. It is unclear why such an arrangement would have been formed as one would generally expect to see integral quoin stones at the corner that add lateral resistance and run in course with the adjoining ashlar, although often project slightly from the building line for aesthetical reasons.

Figure 1: Area of displacement to piers 2. The stonework to these corner piers was noted to course with the main wall panels on the left hand and rear elevations; however both the left hand and right hand piers coursing was mainly mis-aligned with the left hand and right hand ashlar panels.

03. The left hand pier showed a reasonably regular vertical joint with the left hand and rear elevations; these joints however were open in several sections; the pier itself appeared to be reasonably plumb for its full height.

04. The right hand pier showed a widening joint between the pier and the rear elevation with the joint becoming wider towards the top; this movement was pronounced from the string course around first floor level up to the parapet wall; it was noted that the head of the pier appeared to be wedged below the stone blocking course or frieze section forming part of the parapet wall. The joint between the pier and the right hand elevation was noted to be reasonably regular; this joint however was open in several sections up its height.

05. The right hand pier was noted to lean outwards to the right and slightly to the rear with the lean noted from about first floor level.

06. The bay window on the rear elevation showed little signs of recent structural movement with the junctions between the bay structure and the rear elevation, which were noted to be generally intact. Some surface decay and deterioration of the stonework was evident, particularly to the bases of the mullion sections, however there was no signs to suggest recent structural movement. Whilst general weathering has understandably occurred, this is relatively minor considering the age of the building.

07. At high level there was a parapet wall to the rear block formed in three courses of Ashlar blocks with coping stone detail above. To the right hand elevation of this parapet wall, a general bulge was noted along its length with secondary distortion to the rear elevation. Cracking was also evident to the main bulged section and to the secondary distorted section. The mortar joints to this area including vertical perpends were noted to be open.

08. We noted no evidence of recent structural damage to the main elevations forming the left hand wing; the main wall panels themselves appeared to be reasonably plumb.

09. We noted that tie bars were installed to the rear left hand block of the left hand wing complete with pattress plates and are understood to be relatively historic from the record images kindly provided on site for review.

10. The stone work above the entrance Porte Cochere incorporated an ornate band course containing a row of blind quatrefoils, a feature carved stone crest panel to the centre and a parapet detail with battlements complete with embrasures and merlons at the head. Cracking was noted to the arched heads forming the covered entrance on the right hand and left hand elevations with secondary cracking noted to the soffit of the area.

11. Slight cracking was noted to the front elevation to the right of the Porte Cochere above and below window openings; however such cracking did not appear to be recent.

12. A full inspection of the roofs was not possible at the time of our inspection; however there were no reported issues of water ingress.

**Internal**

13. Throughout the interior of the property in the areas of the external areas of concern, we noted no evidence of recent structural damage. DISCUSSION

The property is understood to be nearly 190 years old and retains much of the original features including tall decorative ceilings and areas of ornate stonework to the external elevations.

Our inspection has determined that the rear corner piers or pilasters to the left hand wing are effectively free standing with little, if any tie to the main wall panels. Indications from site measurements taken, suggest that the piers comprise stone blocks which are approximately 150mm on bed and are therefore slender when considering the height of the piers; there was an apparent lack of connection with the main building; notwithstanding the above the piers fortunately seemed to be relatively vertical at the corners in general except for the lean to the rear right hand pier at high level.

We can see no benefit in undertaking a monitoring exercise to determine if movement is progressive or otherwise, however instead we would recommend that remedial works are required to address the movement.

The rear left hand pier shows minimal structural movement; such movement shows mainly as perishing of the vertical joints of the pier to the adjacent wall panels.

In contrast, the rear right hand pier shows leaning along with perishing of the vertical joints with the lean appearing to be restricted, for now, by the stone blocking course of the parapet wall above. However, the stone block against which this corner pier has become wedged is small in comparison with the other blocks of the parapet wall.

The underlying cause of the movement is most probably due to an inherent construction flaw and the free standing nature of the piers appearing to have minimal, if any tie to the adjacent wall panels along with the relative slenderness of the piers. The movement does not appear to be related to foundation settlement or rotation. It is possible that the movement is exacerbated by the poor closure to the heads of the piers and the resultant wash-out/settlement of the rubble fill to the piers.

The parapet wall above the rear left hand area of the left hand wing shows bulging along the length of the right hand wall with secondary distortion to the rear wall and associated cracking. We noted that the parapet wall was constructed with comparatively thin Ashlar blocks with the pointing having noticeably deteriorated; this lack of adhesion between the stones in such a vulnerable location will offer little resistance to movement and will also allow water to penetrate.

It is most probable that the bulging is as a consequence of the block thickness and the deterioration of the mortar along with thermal movement of the right hand (west) wall panel together.

Remedial works shall be required to the parapet wall.

The bay window on the rear elevation showed little signs of recent structural movement. Movement or displacement of stone mullions under compression is usually caused due to either face bedding and orientation of the stone, propagation of natural fissures, overloading or expansion of ferrous metal dowels used to connect the vertical members to the cill stoolings at the base and at other junctions such as horizontal transoms. Although no intervention for realignment is justified at this stage, it would be prudent to either monitor the condition of such important building elements or to undertake remedial works to reinstate the mullion sections particularly at the bases of the deteriorated mullions.

Elsewhere minor cracking was noted to the external elevations to the Porte Cochere and to the wall to the right of the main entrance. REMEDIAL ACTIONS

The remedial works to the rear corner piers can be undertaken successfully with the works to the two individual free standing piers requiring different solutions.

The rear left hand pier requires to be mechanically tied to the adjacent wall panels by diamond drilling through the face of the stone blocks, ensuring minimum percussion and installing long stainless steel tie bars anchoring the same in to the wall panels. The faces of the affected blocks can then be made good using the annulus of the stone (the historic material) removed to conceal the ends of the tie bars in such a way as to offer protection to the tie bar ends and to maintain the appearance of the pier. A degree of honesty yet legibility in the repair will be achieved therefore honouring good conservation principles and practice.

The rear right hand pier should be partially taken down and rebuilt, however, it must be noted that these works will affect the stability of parapet wall above, as the support to that parapet wall will be removed. As such, the remedial works to this pier and the parapet wall should be undertaken concurrently.

In addition the lower section of the rear right hand corner pier should be mechanically tied to the adjacent wall panels as described above for the rear left hand corner pier.

The parapet wall should be taken down from approximately mid-way along the rear elevation and the majority of the right hand elevation. The corner pier should be taken down to just above the string course around first floor level and thereafter the pier should systematically rebuilt incorporating mechanical ties to the wall panels. Once the pier has been rebuilt, the parapet wall should be rebuilt back to line and level including reinstatement of all affected flashings etc.

The annotated repair proposals prepared by Helifix and provided within the Appendix C of this Report, detail a stainless steel sock anchor arrangement which are considered to be an appropriate remedial solution. These proposals should be considered in conjunction with the recommendations made within this Report.

As a sensible and subtle intervention, it is recommended that both corner piers be finished with suitable capping stones to close the heads of the piers to afford suitable protection against water ingress. Limited remedial works are also recommended to the bay window on the rear elevation to restore the bases of the mullions; such works can be suitably colour matched using lime based restoration mortar to blend in with the remainder of the stonework forming this bay window.

Elsewhere to the elevation the various areas of cracking should be addressed; this remedial work should comprise the raking out of the existing mortar as an area opposed to simple line works; thereafter the areas can be repointed in a lime based mortar.

It would be prudent to approach the Local Authority and the National Trust, whom we understand presently own the property to seek approval to undertake the works and to agree the full specification of the remedial works. Whilst repairs to Listed Buildings are permitted without full Listed Building Consent, provided they meet and honour conservation principles and use matching traditional materials and techniques, any amendments or adjustments to such an historic building asset will inevitably require Consent. Early discussions would therefore be advocated and this Report will hopefully act as a ‘springboard’ to facilitate this.

All recommendations made within this Report are based on sound technical judgement on the structural integrity of the elements discussed and remedial works described are deemed essential to safeguard the ongoing survival of part of the impressive heritage asset that is, Ilam Hall. We feel the proposals demonstrate compliance with the tenets of conservation practice and principles, which demand a minimum intervention approach and maximum retention of historic fabric throughout.

The conservation discussion document which is included within the Appendix D of this Report for further reference helps guide our decision making when dealing with such sites. CONCLUSIONS

Having carefully reviewed the matter we have drawn the following conclusions:

1. The damage noted to the corner piers is such that monitoring will delay the inevitable remediation actions required.
2. The rear corner piers require remedial works to be undertaken.
3. The rear left hand pier should be mechanically tied to the adjacent wall panels.
4. The rear right hand corner pier should be partially taken down and rebuilt and tied to the adjacent wall panels.
5. The parapet wall above the rear block should be partially taken down and rebuilt; these works are to be carried out in conjunction with the works to the rear right hand corner pier.
6. The rear bay window would benefit from remedial actions to restore the eroded base sections of the mullions.
7. The areas of cracking to the elevations are to be raked out and repointed as an area remedial action and not just simple line works.
8. Formal Approvals shall be required to undertake the remedial works from both the Local Authority as well as the building owners, The National Trust.
9. Specialist contractors should be engaged to undertake the works given the detail and quality of the damaged areas and the Listed status of the property. BUDGET COSTS

We have carefully considered the costs for the remedial works and provide the following budget costs based on works of a similar nature with which we have recently been involved.

These budget costs include all required access equipment, scaffold etc but exclude costs associated with the contractor accommodation for the duration of the works are excluded:

Works to rear right hand pier:

- Structural intervention (mechanical ties) £6,000.00
- Dismantlement and rebuilding etc £7,500.00

Works to rear left hand pier:

- Structural intervention (mechanical ties) £7,500.00

Works to parapet wall:

- Dismantling and rebuilding including ties etc £7,000.00

Repointing works:

- Assuming an area of 20 m²: £2,000.00

TOTAL BUDGET COSTS £30,000.00 plus VAT

In addition to the contractor costs Local Authority fees shall be required along with decoration costs and professional fees.

Prepared by: P A Hucks C.Eng M.I.Struct.E B.Sc.(Hons) APPENDIX A

Historic photographs – provided by Youth Hostel Association A1. Image of the original 1820’s Ilam Hall – note Porte Cochere to the far right corner.

A2. Copy of historic plan showing the original ground floor plan – note Porte Cochere and areas shown now demolished. APPENDIX B

Photographs – taken during site inspection on 9 June 2014 B1. View of Ilam Hall and the left hand wing – note Porte Cochere to the right of the image and the rear block and corner projecting pier to the left of the image.

B2. View of front and right hand elevation of the Porte Cochere and the remainder of the property running off to the right. B3. View of rear elevation of the rear block.

B4. View of the upper part of the rear elevation of the rear block including the parapet. B5. View of left hand elevation of the rear block.

B6. Detail view of rear left hand corner pier to the left hand elevation of the rear block – note the ties and pattress plates. B7. View of rear right hand corner pier to the rear block.

B8. Detail view of right hand face of the rear right hand corner pier to the rear block. B9. Detail view of rear face of the rear right hand corner pier to the rear block – note the high level rotation, the tie bar and pattress plate and the apparent wedging effect with the parapet wall string course.

B10. Further view of the rear face of the rear right hand corner pier to the rear block. B11. Internal view towards the rear left hand corner of the rear block – note bay window on rear elevation.

B12. View of right hand elevation above Porte Cochere. B13. View of damage to soffit within the Porte Cochere.

B14. View of left hand elevation of the Porte Cochere. APPENDIX C

Proposed Repair Solution - Helifix Sockfix Tie APPENDIX D

Conservation Discussion Document